Witzel et al. U.S. Pat. No. 4,920,959 discloses an external fixture which is relatively cumbersome. It includes twin-rod holders, a pair of longitudinal fixture frame rods, a bone screw for each rod holder, and operating screws for fixing the bone screws to the rods. A disadvantage of the individual twin-rod holders (i.e., the clamping elements) is that they apparently mount onto the longitudinal rods from only the ends of the rods.
Swiss Patent No. CH 632 658 discloses an implant for fixing bones. The quality of the disclosed locking device depends directly on the pretensioned force, which can be realized between the Briden body and the bone. Here also, if the implant is used as a clamp, the individual clip body (i.e., clamp element) apparently mounts onto two parallel longitudinal rods from only the ends of the rods (lateral mounting is apparently not possible). This mounting may be difficult to realize in the case of a freehand application, particularly a percutaneous and minimally invasive application, and represents a major disadvantage.
On the other hand, Vignaud et al. U.S. Pat. No. 5,290,288, WO 94/01049, and French Patent No. FR 2 775 587 all disclose open clamps in which a longitudinal carrier can be laterally mounted. However, they all have the disadvantage of requiring an additional element (e.g., a nut) for their fixation. Furthermore, the clamp holding device is the bone screw itself, which typically must first be fixed in the bone before the longitudinal carrier can be placed on the bone screw.
Finally, WO 95/13754 discloses a clamp in which a longitudinal rod can be introduced laterally into an open channel of the clamp. The rod can then be secured by means of a set screw, which passes through the clamp. However, the set screw has only this one function and cannot be used, for example, as a bone screw that could fasten the whole construct at the bone. The same is also true for the holding device disclosed in German Patent No. DE 195 34 136.
Accordingly, known devices can be quite complicated having little flexibility with respect to their application.
In view of the foregoing, it is an object of the invention to provide a device that has a very simple structure and that can be used flexibly and in minimally invasive surgical techniques.